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New case reports bolster the argument that oral anticoagulation therapy can resolve valve thrombosis following transcatheter aortic valve implantation (TAVI), researchers suggested.

The current antithrombotic treatment following TAVI is aspirin plus clopidogrel for three to six months, but this antiplatelet therapy is not evidence-based. As case studies emerge indicating post-TAVI thrombosis can be resolved with warfarin and other vitamin K antagonists, investigators have been questioning this standard treatment.

Last month, Italian researchers out of Milan published three such cases in the Journal of the American College of Cardiology. This month, three new cases also out of Italy and also published as research correspondence in the Journal of the American College of Cardiology, lend more evidence that oral anticoagulation therapy resolves post-TAVI thrombosis.

The three new cases studies, presented by Linda Cota, MD, and colleagues from Clinica Montevergine in Mercogliano, Italy, detail "bioprosthesis dysfunction due to leaflet thrombosis after [TAVI]."

Each patient received the Sapien XT valve, which is "manufactured in the same way as conventional aortic bioprostheses," and should therefore have "similar thrombogenicity," Cota and colleagues wrote.

"For this reason, after [TAVI], it is common practice to prescribe antiplatelet therapy and no oral anticoagulation."

But in all three of these cases, and in the previous three cases reported from Milan and involving the Sapien valve, the thrombosis was resolved with oral anticoagulation therapy, "and the patients did not require open-heart surgery," Cota and colleagues noted.

The first case involved an 80-year-old woman on aspirin, who became symptomatic at 10 months post-procedure. She exhibited dyspnea and had a mean pressure gradient of 54 mmHg (compared with 10 mmHg at discharge and 12 mmHg at 1 month).

Researchers suspected thrombosis when transesophageal echo (TEE) showed two leaflets fused. After 3 months of oral anticoagulation therapy, her mean pressure gradient was 13 mmHg, TEE was normal, and she was asymptomatic.

The second case, of an 81-year-old man on aspirin, also involved fused leaflets on TEE at 4 months when the patient returned with dyspnea. He exhibited an elevated mean pressure gradient of 51 mmHg, but 2 months after oral anticoagulation therapy, the mean pressure gradient dropped to 9 mmHg and TEE showed "restored bioprosthesis function."

Case No. 3 detailed the experience of a 74-year-old woman on dual antiplatelet therapy whose TEE at 2 months post-procedure "showed a suspicion of thrombotic apposition blocking the movement of a bioprosthesis leaflet."

Two months of anticoagulation therapy restored her to normal gradients (9 mmHg) and she was asymptomatic.

"We believe that this report can be hypothesis-generating to design a trial aimed at identifying the proper antiplatelet or anticoagulation therapy after [TAVI] and to identify therapy for bioprostheses thrombosis," they concluded.

Similarly, the Milan investigators of the previous three cases noted that "although there have been reports of reversible dysfunction of surgical bioprostheses with anticoagulation, the optimal antithrombotic therapy after surgical or transcatheter bioprostheses implantation is still uncertain."

They also called for "further investigation on the optimal antithrombotic strategy after TAVI."

From the American Heart Association:

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